Policy proposal - CPP_PREDEFINES

[Zack Weinberg]

I'd like this to become official GCC policy: Beginning now, no new
port may include any symbol in CPP_PREDEFINES which is outside the C89
reserved name space.

That means all -D entries must begin with either two underscores, or
an underscore and a capital letter.  __unix is acceptable, unix is
not.

As an example, the (relatively new) ia64 ports define 'hpux', 'unix',
'ia64', and 'linux' depending which port they are.  We may be stuck
with these now, but let's not continue to include them in brand-new
ports.

zw